To solve this, you would set up the equation to find the arithmetic mean of the data. This equation is (53+83+67+73+x)/5=70, where x=the score of the fifth exam. First, you combine the constants to get (276+x)/5=70. Then, multiply both sides by 5 to get rid of the denominator, to give you 276+x=350. Then subtract 276 from each side to get x=74. So, Thanh needs to score a 74 on his last exam to get a 70 in the class.
